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Stationary Hydraulic Riveter.                 313

of holes. Considerable economy results from the application of
this machine, which is very well designed in Plate XIV.

Summing up, the great desiderata in boiler drills are rapidity
of adjustment and withdrawal of tool, and where possible the
introduction of multiple drilling.

Hydraulic Riveting, Machines.—It is to the late Mr.
Ralph H. Tweddell that the honour of introducing hydraulic
riveting belongs. No other method is now used, excepting
pneumatic and electric contrivances, which are now being
more employed: but steam riveting is entirely obsolete. The
advantage of hydraulics for riveting is very great: it is a power
that can be conveyed to great distances without appreciable loss,
it can be stored till wanted, and the steady and known pressure
on the rivet-head, coupled with the increase due to absorption
of the momentum of the accumulator weight at the moment of
closing, is just the action most desired. {See Appendix I., p. 754.)

Large Fixed Riveter.—This machine, on TweddelPs
system, is shewn in Fig. 298. The standards A and B are securely
connected by two bolts at c, and well designed to resist the
stresses caused in closing. A supports the cylinders, while B
serves as ' dolly,' carrying the tail cup M, and presenting a
nearly flush top surface, for the purpose of getting into corners.
The riveting cylinder y, carrying the heading cup, rides upon
a fixed ram x, and within Y is placed the ram u, which advances
the annular plate-closing tool v. The auxiliary ram x, of piston
form, receives pressure on either face for advance or return :
and the tank D, placed 20 feet above the top of the machine,
supplies the cylinders x and u with low-pressure water. The
pipe E carries this water to cylinder x, and the branch pipe R
passes to u, the check-valves Q and s in each case preventing
return excepting through the exhaust pipe L. The latter com-
municates with each of the piston valves, p, o, N, as does the
pressure pipe j; P being connected to the back end of the
cylinder x, through the pipe a: o with the cylinder u through
pipe A : and N with the cylinder x: while b is a constant pressure
pipe connecting j and the front end of x. K is a stop valve, and
z an overflow pipe.

We can now understand the action of the machine.    The